Jaiminīya Upaniṣad Brāhmaṇa 3.14.7

3.14.7

tasyedam mānuṣanikāśanam aṇḍam udare 'ntas sambhavati
tasyordhvam annādyam utsīdati stanāv abhi
sa yad ājāyate 'thāsmai mātā stanam annādyam prayacchati /

This human-resembling egg forms within the belly;
its food-essence rises upward toward the breasts;
when he is born, then the mother offers him the breast, the food-essence.